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Abstract

Objective—To estimate the prevalence of radiographic abnormalities (lesions) in Thoroughbred racehorses at 2-year-old in-training sales and determine whether these lesions and 1-furlong presale workout times were associated with subsequent racing performance.

Design—Retrospective cohort study.

Animals—953 Thoroughbreds.

Procedures—Repository radiographs of carpal, metacarpophalangeal and metatarsophalangeal (fetlock), stifle, and tarsal (hock) joints were examined. Horses with lesions were classified by lesion type and location. Race performance variables were compared between horses with and without lesions and between horses categorized by 1-furlong presale workout times (< or ≥ 11 seconds).

Results—299 horses had ≥ 1 lesion, and 654 had no lesion detected. Odds of starting a race and of earning money racing were lower for horses with any lesion and lower for horses with proximal phalangeal dorsoproximal articular margin chip fracture, proximal sesamoid bone fracture or sesamoiditis, or wedge-shaped central or third tarsal bones, compared with horses that had no lesion. For horses that raced, proximal phalangeal dorsoproximal articular margin chip fractures were associated with lower lifetime earnings, and flattening of the medial femoral condyle was associated with fewer 3-year-old racing starts, compared with values for horses that had no lesion. Horses with workout times < 11 seconds had greater odds of having lifetime starts, lifetime earnings, and maximum purse above threshold (median) values than did horses with slower workout times.

Conclusions and Clinical Relevance—No radiographic lesions prevented all affected horses from racing. Among horses that raced, few differences were found in performance for horses with and without lesions.

Full access
in Journal of the American Veterinary Medical Association

Abstract

OBJECTIVE To evaluate biomechanical properties of intact feline mandibles, compared with those for mandibles with an experimentally created osteotomy that was stabilized with 1 of 2 internal fixation configurations.

SAMPLE 20 mandibles from 10 adult feline cadavers.

PROCEDURES An incomplete block study design was used to assign the mandibles of each cadaver to 2 of 3 groups (locking plate with locking screws [locking construct], locking plate with nonlocking screws [nonlocking construct], or intact). Within each cadaver, mandibles were randomly assigned to the assigned treatments. For mandibles assigned to the locking and nonlocking constructs, a simple transverse osteotomy was created caudal to the mandibular first molar tooth after plate application. All mandibles were loaded in cantilever bending in a single-load-to-failure test while simultaneously recording load and actuator displacement. Mode of failure (bone or plate failure) was recorded, and radiographic evidence of tooth root and mandibular canal damage was evaluated. Mechanical properties were compared among the 3 groups.

RESULTS Stiffness, bending moments, and most post-yield energies for mandibles with the locking and nonlocking constructs were significantly lower than those for intact mandibles. Peak bending moment and stiffness for mandibles with the locking construct were significantly greater than those for mandibles with the nonlocking construct. Mode of failure and frequency of screw damage to tooth roots and the mandibular canal did not differ between the locking and nonlocking constructs.

CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that both fixation constructs were mechanically inferior to intact mandibles. The locking construct was mechanically stronger than the nonlocking construct.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate subchondral bone density patterns in elbow joints of clinically normal dogs by use of computed tomographic (CT) osteoabsorptiometry.

Sample Population—20 cadaver forelimbs from 10 clinically normal dogs.

Procedure—Each elbow joint was imaged in parasagittal and transverse planes of 1.5-mm thickness. Slice data were converted to dipotassium phosphate equivalent density (PPED) values. Sagittal, parasagittal, and transverse medial coronoid process topographic maps were constructed. Defined zones were created for each of the 3 CT planes, and confluence and peak PPED values were determined.

Results—The lowest PPED value was 340 mg/ml (articular and subchondral confluence), and the highest was 1780 mg/ml (peak subchondral density). Detectable effects of joint laterality were not found in the confluence or peak PPED measurements or in the peak-to-confluence PPED ratio for all 3 CT planes. Significant differences were found among zones in all 3 planes for confluence and peak PPED measurements and between sagittal and transverse planes for peak-to-confluence PPED ratios. Subjectively, the pattern of density distribution among dogs was fairly consistent for the sagittal and parasagittal slices. Three specific patterns of density distribution were apparent on the transverse topographic maps of the medial coronoid process that corresponded to conformational differences.

Conclusions and Clinical Relevance—The use of CT osteoabsorptiometry provides a repeatable technique that can be used to noninvasively examine bone density and the effects of stress acting on joints in vivo. Variability in density values for any of the CT planes was not identified among clinically normal dogs. (Am J Vet Ress 2002;63:1159–1166

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE

To evaluate and quantify the kinematic behavior of canine mandibles before and after bilateral rostral or unilateral segmental mandibulectomy as well as after mandibular reconstruction with a locking reconstruction plate in ex vivo conditions.

SAMPLE

Head specimens from cadavers of 16 dogs (range in body weight, 30 to 35 kg).

PROCEDURE

Specimens were assigned to undergo unilateral segmental (n = 8) or bilateral rostral (8) mandibulectomy and then mandibular reconstruction by internal fixation with locking plates. Kinematic markers were attached to each specimen in a custom-built load frame. Markers were tracked in 3-D space during standardized loading conditions, and mandibular motions were quantified. Differences in mandibular range of motion among 3 experimental conditions (before mandibulectomy [ie, with mandibles intact], after mandibulectomy, and after reconstruction) were assessed by means of repeated-measures ANOVA.

RESULTS

Both unilateral segmental and bilateral rostral mandibulectomy resulted in significantly greater mandibular motion and instability, compared with results for intact mandibles. No significant differences in motion were detected between mandibles reconstructed after unilateral segmental mandibulectomy and intact mandibles. Similarly, the motion of mandibles reconstructed after rostral mandibulectomy was no different from that of intact mandibles, except in the lateral direction.

CONCLUSIONS AND CLINICAL RELEVANCE

Mandibular kinematics in head specimens from canine cadavers were significantly altered after unilateral segmental and bilateral rostral mandibulectomy. These alterations were corrected after mandibular reconstruction with locking reconstruction plates. Findings reinforced the clinical observations of the beneficial effect of reconstruction on mandibular function and the need for reconstructive surgery after mandibulectomy in dogs.

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE To describe the torsional and axial compressive properties of tibiotarsal bones of red-tailed hawks (Buteo jamaicensis).

SAMPLE 16 cadaveric tibiotarsal bones from 8 red-tailed hawks.

PROCEDURES 1 tibiotarsal bone from each bird was randomly assigned to be tested in torsion, and the contralateral bone was tested in axial compression. Intact bones were monotonically loaded in either torsion (n = 8) or axial compression (8) to failure. Mechanical variables were derived from load-deformation curves. Fracture configurations were described. Effects of sex, limb side, and bone dimensions on mechanical properties were assessed with a mixed-model ANOVA. Correlations between equivalent torsional and compressive properties were determined.

RESULTS Limb side and bone dimensions were not associated with any mechanical property. During compression tests, mean ultimate cumulative energy and postyield energy for female bones were significantly greater than those for male bones. All 8 bones developed a spiral diaphyseal fracture and a metaphyseal fissure or fracture during torsional tests. During compression tests, all bones developed a crushed metaphysis and a fissure or comminuted fracture of the diaphysis. Positive correlations were apparent between most yield and ultimate torsional and compressive properties.

CONCLUSIONS AND CLINICAL RELEVANCE The torsional and axial compressive properties of tibiotarsal bones described in this study can be used as a reference for investigations into fixation methods for tibiotarsal fractures in red-tailed hawks. Although the comminuted and spiral diaphyseal fractures induced in this study were consistent with those observed in clinical practice, the metaphyseal disruption observed was not and warrants further research.

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE

To evaluate the biomechanical properties of the mandibles of cats with experimentally created osteotomies simulating oblique ramus fractures, which were stabilized with malleable L-miniplates with either locking screws [locking construct (LC)] or nonlocking screws [nonlocking construct (NLC)], compared with those for intact mandibles.

SAMPLES

20 mandibles from 10 adult cat cadavers.

PROCEDURES

A block study design was adopted to allocate the mandibles of each cadaver to 2 of the 3 test groups (LC, NLC, or intact mandible). Mandibles within each cadaver were allocated systematically to a test group. For mandibles assigned to an LC and an NLC, a complete oblique osteotomy was performed from the mid rostral aspect of the ramus in a caudoventral direction. All mandibles were loaded in a single-load-to-failure test through cantilever bending. Load and actuator displacement were recorded simultaneously. Mode of failure and radiographic evidence of damage to tooth roots and the mandibular canal were evaluated. Biomechanical properties were compared among the groups.

RESULTS

No iatrogenic tooth root damage was evident, but all mandibles with an LC and an NLC had evidence of screw invasion into the mandibular canal. Plated mandibles had significantly less stiffness and bending moment than intact mandibles. Stiffness was not significantly different between the LC and the NLC; the NLC had a greater bending moment at failure than the LC. The pre-yield stiffness of plated mandibles decreased when the number of screw holes overlapping the mandibular canal increased.

CLINICAL RELEVANCE

The use of a malleable L-miniplate in a caudal mandibular fracture model is feasible. Both the LC and the NLC were inferior mechanically to intact mandibles. Type of construct used did not affect the construct stiffness significantly in tested mandibles.

Open access
in American Journal of Veterinary Research

Abstract

Objective

To assess tendon morphology and non-reducible crosslink concentration, and associations of these findings with horse age and previously reported mechanical and ultrasonographic findings.

Sample Population

Superficial digital flexor tendon samples were obtained from 23 horses aged 2 to 23 years. The tendons had undergone ultrasonography and were submitted to biomechanical testing in the physiologic range prior to sample acquisition.

Procedure

Samples were sectioned in a transverse plane; then dorsal, palmar, central, lateral, and medial regions were evaluated for fascicle cross-sectional area (CSA), septal width, and vessel density (the product of vessel numbers and vessel CSA per field). Contiguous samples were analyzed for collagen crosslinking.

Results

Central fascicles were significantly larger than fascicles in other tendon regions. Fascicle CSA decreased significantly with increasing age. Because total tendon CSA is unrelated to increasing age, fascicle numbers appeared to increase with increasing age. Regional or age effects on septal width were not found. There was no age or regional effect on vessel numbers, density, or fractional area.

Fascicle CSA was positively correlated with total tendon CSA; fascicle CSA was negatively correlated with elastic modulus. Hydroxypiridinium concentration tended to increase with increasing horse age; this effect was associated with a positive correlation between hydroxypiridinium values and elastic modulus.

Conclusions

Equine superficial digital flexor tendon undergoes an increase in structural organization and an increase in nonreducible crosslinks with maturation and aging. These changes are associated with an increase in elastic modulus. (Am J Vet Res 1997; 58:425–430)

Free access
in American Journal of Veterinary Research

SUMMARY

Ultrasonographic cross-sectional area (csa) measurements of equine superficial digital flexor (sdf) tendon were obtained to determine the feasibility of ultrasonography for csa measurement of tendon in vivo and in vitro. Ultrasonographic measurements were compared with a more traditional csa measurement method, ink-blot analysis. In addition, values for ultrasonographic sdf tendon mean echogenicity were obtained in vivo and in vitro. The left forelimb sdf tendons of 23 horses were evaluated ultrasonographically. Cross-sectional images were acquired at 4-cm intervals distal to the base of the accessory carpal bone (dacb) to the level of the proximal sesamoid bones while horses were standing squarely. After euthanasia, the left forelimbs were mounted in a materials testing system (mts) and loaded under tension to standing load. Ultrasonographic images were again acquired at the same locations. The ultrasonographic images were digitized, and values for ultrasonographic csa and mean echogenicity were obtained for each level.

Immediately after mechanical testing, a 1-cm-thick transverse section of sdf tendon at 12 cm dacb was removed. Three ink blots were prepared from each end of the removed tendon section and digitized. The 6 csa values were averaged to generate a value for morphologic csa for each sdf tendon at 12 cm dacb.

Standing ultrasonographic tendon csa at 12 cm dacb was consistently smallest (mean ± sd csa = 86 ± 11 mm2), followed by mts ultrasonographic csa (mean, 95 ± 12 mm2), ink-blot morphologic csa being largest (mean, 99 ± 15 mm2). Comparison of standing and mts ultrasonographic csa values at 12 cm dacb revealed a strong positive linear correlation between methods (R 2 = 0.74, P = 0.001). Comparison of ink-blot csa at 12 cm dacb with standing and mts ultrasonographic csa revealed strong positive linear correlations (R 2 = 0.64, P = 0.001 and R 2 = 0.72, P = 0.001, respectively).

For ultrasonographic mean echogenicity, standing values insignificantly exceeded mts values at each level. The authors conclude that ultrasonography is a useful technique for the noninvasive assessment of sdf tendon csa that can be applied in vivo and in vitro.

Free access
in American Journal of Veterinary Research

SUMMARY

Results of studies in human beings and other species have indicated that aging significantly influences the strength, modulus of elasticity, and energy storage ability of tendon. We wanted to determine the effects of aging on the material and ultrasonographic properties of equine superficial digital flexor (sdf) tendon. Ultrasonographic measurements of left forelimb sdf tendon cross-sectional area and mean echogenicity were made in 23 standing horses ranging in age from 2 to 23 years. All horses had not been in work for a minimum of 6 months prior to the study. After euthanasia, left forelimb bone-muscle-tendon-bone specimens were mounted in a materials testing system. The sdf tendon was cyclically loaded sinusoidally 100 times at 0.5 Hz from 1.5 to 5.0% strain, then was submitted to 10-minute creep-and-stress relaxation tests. Modulus of elasticity, load at 3% strain, and creep-and-stress relaxation were determined for each specimen. A significant positive correlation was found between elastic modulus and age. Correlation was not found between age and sdf tendon cross-sectional area or mean echogenicity. When 2-year-old horses were compared with older horses, the latter had tendons with a significantly (P = 0.007) greater modulus of elasticity. The authors conclude that increasing age through maturity is associated with a corresponding increase in equine sdf tendon elastic modulus.

Free access
in American Journal of Veterinary Research